The term "concomitant syndrome of tumor" means symptoms accompanying various malignant tumors other than the direct symptoms, for example, cachexia, abnormalities in blood such as leukocytosis, failures in the homeostasis of bodily fluids typically exemplified by electrolyte abnormality, metabolic error such as hypoglycemia and diabetes, skin lesion, neurologic manifestation, serum protein abnormality, renal disorders, osteoarticular disorders, hyperenergia in association with the excessive secretion of adrenal cortex hormone, etc. These symptoms frequently arise in series. Among these symptoms, cachexia and electrolyte abnormality are the major ones which are known as the serious causes of the death of patients with cancer similar to respiratory failure, circulatory failure, digestive diseases, hemorrhage, systemic infection, etc.
The term "cachexia" means a systemically depressed state due to a chronic disease and its main symptoms include serious weight loss, inappetence and anemia. As typical examples of cachexia, there have been known cancerous cachexia, infectious cachexia, thyroid cachexia, etc.
Among all, it is considered that cancerous cachexia is a hindrance in the treatment for cancer, since it depresses the tolerance to chemotherapy or radiotherapy [Johanna T. Dwyer, Cancer, 43, 2077 (1979); Sarah S. Donaldson et al., Cancer, 43, 2036 (1979), etc].
To treat the concomitant syndrome of tumor, it has been a practice, for example, to administer various replenisher solutions and bone resorption inhibitors in the case of electrolyte abnormality. However these treatments are symptomatic ones which cannot suppress the production of causal substances originating in malignant tumors. Thus it is impossible to sufficiently cure the concomitant syndrome of tumor thereby.
Regarding the treatment of cachexia, on the other hand, it has been a practice to improve the nutritional status of patients by the administration of a high fat diet or a high saccharide diet, high caloric fluid therapy, blood transfusion, etc. However, these treatments serve merely as symptomatic therapy and can scarcely achieve any sufficient effect. Further, antitumor agents employed at present frequently induce serious side-effects and none of them is efficacious in the amelioration of cachexia. Accordingly, it has been urgently required to develop drugs for curing and ameliorating cachexia.
By the way, it has been known in general that some vitamin D derivatives show various physiological activities, for example, regulation of calcium metabolism, inhibition of the multiplication of tumor cells, induction of the differentiation of tumor cells, immunomodulation, etc. It is known that 22-oxa-vitamin D derivative having an oxygen atom at the 22-position, from among these vitamin D derivatives, exhibits only an extremely weak side-effect of inducing hypercalcemia which is commonly caused by other vitamin D compounds. Thus it is reported that this 22-oxa-vitamin D derivative is effective against psoriasis, secondary hyperparathyroidism, etc. (see, for example, Japanese Laid-Open Patent Publication No. Sho 63-183534 and Japanese Patent Publication No. Hei 6-86382). It is also known that this 22-oxa-vitamin D derivative has an antitumor effect. However, it has never been reported that this compound is effective against the concomitant syndrome of tumor such as cachexia.
An object of the present invention is to provide a drug which can cure the concomitant syndrome of tumor, in particular, cachexia or ameliorate the symptoms thereof.